Computer game programs are run on a computer game system which comprises a game computer having a microprocessor for executing the program, an input device such as a joystick for a user to control the execution of the program, and an output device such as a monitor or television set (VDU) for providing the user with visual and audio output signals. The programs are usually stored on magnetic tape, on floppy disks or compact disks, or in ROM cards which are generally referred to as cartridges, so that different computer games can be played.
In systems using a cartridge, the game computer and the cartridge are provided with complementary connectors, such as pin or slot connectors, for connecting together their corresponding address, data and control buses The connectors are separable so that the cartridge can be replaced by another one carrying a different game program.
A typical computer game is divided into different levels or stages and normally starts to play from the beginning of level one. Some computer games provide a CONTINUE function which allows a user to start the games from the beginning of a particular level which the user has managed to reach in the previous play. However, the CONTINUE function is usually available only for a limited number of times, and the user is not allowed to start the game at any desired instant within the level previously reached. Once the CONTINUE function is no longer available, the user must start the game from the beginning of level one. Even when the CONTINUE function is still available, the user has to go through again the beginning part of the last level which has previously been successfully played.